A wide variety of control systems are known in the art for safely controlling passenger carrying vehicles traversing a guideway or the like. One of the prime requirements of these systems is to avoid rear end type collisions. The conventional manner in which such collisions are avoided is by requiring a minimum safe headway between vehicles at all times. The minimum safe headway is computed such that if a preceding vehicle comes to an immediate stop, the following vehicle will, within the safe headway separation distance, be able to come to a safe stop without impacting the preceding vehicle. Those systems known in the prior art can be characterized as manual, semi-automatic and automatic systems. In each of these systems information is communicated to the vehicle, from equipment on the wayside, with regard to the actual separation between that vehicle and a leading vehicle. Based upon that information the following vehicle then can select the appropriate speed such that for the selected speed the actual headway corresponds to a safe stopping distance. This necessarily implies that each of the vehicles is capable of traveling at each of a predetermined plurality of speeds and can accurately be controlled to maintain that speed. The trend has been for the equipment to assume more and more responsibility and thus leave less and less responsibility for any operator, including systems in which the operator has actually been eliminated and thus the equipment itself assumes the responsibility for governing movement of the vehicle. As a result this equipment, especially in the case where no operator is present, necessary to maintain safe operation of the vehicle can be costly, complex and bulky. For systems in which each of the vehicles is large compared to the passenger load it carries this presents little or no difficulty. However, it is often desired to provide equipment for governing movement of vehicles in which prior art equipments would actually occupy a large percentage of space available on board the vehicle and thus render such a system uneconomic in that each of the vehicles would have restricted load carrying capacity. The reason for this large amount of equipment should be apparent to those familiar with the requirements imposed on this equipment. In particular, the equipment must be capable of receiving and decoding signals regarding specific desired speeds, translate the decoded information into controls for controlling the propulsion equipment on board the vehicle, in some cases transmit to the wayside the signals indicative of the condition of the equipment on board the vehicle, compare actual vehicle speed to the desired vehicle speed and control propulsion as well as braking equipment on board the vehicle to bring the two speeds into coincidence and accomplish all of the foregoing functions in a fail safe manner in which any failure of any equipment or portion thereof occurs in a manner to maintain the safety of the vehicle.
Those skilled in the art are aware that many of the aforementioned control systems known to the art are based upon vehicle detection as a result of the interaction between steel wheels riding on steel rails. However there is also a noticeable trend in the field for the use of vehicle-roadway combinations which do not provide this vehicle detection capability. Thus, for control systems in this context some other arrangement must be made for detecting the presence of a vehicle in a predetermined location.
It is therefore an object of the present invention to provide a control system in which the control equipment on board the vehicle is vastly simplified in comparison with that required in the prior art. It is another object of the present invention to provide such a control system in which the simplified control apparatus on board the vehicle eliminates the necessity for on-board failure checking systems along with the attendant complexity of those components. It is still another object of the present invention to provide a control system of the foregoing type which is operative for combinations of vehicle and roadway which do not include a steel wheel-steel rail.